Aspects of the Impacts of Mouse (Mus musculus) Control on Skinks in Auckland, New Zealand. A thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Conservation Biology At Massey Universi~I', Auckland, New Zealand Christopher James Wedding 2007 Shore skink By Oscar Matakana Primary School (2007). 11 Abstract Conservation in New Zealand has a strong focus on pest control and eradication. However, a growing number of eradication attempts have failed to extirpate, or prevent reinvasions of house mice (Mus musculus). This thesis experimentally examined aspects of lizard ecology in relation to mice and the use of brodifacoum for mouse control. Shore skinks ( Oligosoma smithi) were surveyed in three grids under different levels of mouse control (long term. LT. short term. ST and uncontrolled. UC). Skink capture rates. demographics and body condition were recorded on a monthly basis (November 2006 to June 2007). Skink capture rates were highest in the LT and lowest in the UC grid. Twice as many juveniles were caught in the LT than ST and UC sites: however proportions of neonates were not significantly different. Proportions of recaptured skinks within LT and UC grids peaked in February. whereas the ST grid showed peaks corresponding with troughs in mouse abundance. Mice were snap-trapped and gut contents were analysed from 50 per month (February to May). Skink remains were identified from 14 mice. Impacts of brodifacoum on shore skinks in situ as well as rainbow skinks (Lampropholis delicata) in captivity were investigated. Skink visitation rates to brodifacoum bait stations were quantified using tracking cards. Skinks were assessed for signs of ill health. Shore skink tracking rates reached 81 %. One skink was observed consuming bait directly. Rainbow skinks showed higher tracking rates inside stations without bait than baited. either species indicated any sign of ill health. Captive rainbow skinks were supplied with brodifacoum cereal blocks or brodifacoum-loaded Ill mealworms. Rainbow skinks were not observed to directly ingest brodifacoum and sho\ved no affects on weight gain or behaviour. Results suggest that mice arc predators of skinks. pat1icularly during and shortly after skink birthing period. This has important implications for mainland conservation efforts where mice arc more difficult to control. and particularly for rare and cryptic lizard species. \Jative !izards may be significant vectors of brodifacoum. \Yherc they arc abundant. Although nrnuse eradications should he attempted \\hen possible. further research into acute toxicity and sub-lethal effects or brodifacoum is urgently required. IV Acknowledgements This thesis has been an amazing journey. and after many years of study in Palmerston North and Auckland. ifs suddenly come to an end . I am extremely grateful to so many people who· ve supported and encouraged me along the way. Firstly. my supervisors Dianne Brunton and Weihong Ji , who provided guidance, encouragement and support fo r my research interests .. ... .. And then fu11her guidanc e. encouragement and support as my focus sub seq uentl y drifted fro m trackin g mice and forest geckos up trees at ni ght to hunting skinks by day. A big thank yo u to all those who helped me out at the Ocean Beac h dunes: up to eight and a half hours in the blistering sun with the smelly .. Bag o· Mic e .. wasn·t always glamorous. but definitely memorable! Thanks heaps to Mark Delaney. Haden Hend erson. Amy MacDonald, Marleen Baling. Mark Seabrook-Dav iso n. Kara Pra nk erd. Mike Anderson and Wei hong Ji. I am particularly gratefu l to all of those who helped me with the ra inbow skink work. Very special thanks to Di ann e Brunton. who provided me with happy skink hunting grounds. A big thanks must go to Marl ee n Balin g. Jo Peace. Mark Delaney, Mark Seabrook Davison, Dylan van Winkel, Manuela Barry and Ben Barr fo r their time and skink-hunting skills when I suddenly needed 72 rainbow skinks. I am also very grateful to Brett Gartrell (IV ABS, Massey University) for hi s invaluable animal ethics advice on anticoagulant toxicity in reptiles, and Weihong Ji , for humanely euthanising skinks when it was time. A hu ge thank yo u must also go to Penny Fisher and Lynn Booth (Landcare Research, Lincoln) for their very helpful comments and suggestions on the V rainbow skink experimental design. and to the toxicology team at Landcare Research. Lincoln, for processing my skink and mealworm samples. Thank you very much to those who read through draft manuscripts and offered plenty of tips and suggestions. Thanks Rosemary Barraclough. Marleen Baling (and thanks for the use of your books on your bookshelf). Kevin Parker, Manuela Barry (thank you also. Manu, for your time and patience in providing me with a crash course in SPSS), Mike Anderson. Monique Jansen Van Rensburg (and thank you also Monique. for the huge help with the formatting). Jo Peace. Mark Seabrook-Davison. Luis Ortiz Catedral. Stephanie Fill. Kara Prankerd and of course my supervisors Weihong and Dianne. Thank you very much to the tremendous support I received from the Auckland Regional Council. Special thanks must go to Graham Ussher. for invaluable advice. encouragement and suppo11. Graham was largely responsible for my eventual move from forest geckos in Possum Gully to shore skinks at Ocean Beach. Huge thanks to Maurice Puckett and Colin Ward, Tawharanui Rangers, for great laughs and conversations which made some truly memorable and thoroughly enjoyable stays at the vol-hole. Thank you also to Tim Lovegrove (ARC Heritage) and Matt Maitland (TOS project manager), for providing advice and much needed support for this project. A huge thank you to all the awesome friends l"ve made at the Ecology and Conservation Group. Thanks to Jo Peace, Monique Jansen Van Rensburg and Anna Gsell for having the sixth sense of knowing when it was coffee time. Thank you also to Mark Delaney, Mark Seabrook-Davison, Birgit Ziesemann, Monique Jansen Van Rensburg, Marleen Baling, Mike Anderson, Manuela Barry. Kevin Parker. Dylan van VI Winkel. Ben Barr and Karen Stockin for being there and being positive and enthusiastic about this project. Very special thanks to mum and dad. for your tremendous support and home-cooked meals. Thank you so much mum. for making sure I was ahvays eating right. Dad. thanks so much for being there when I suddenly needed to build 120 \\ooden pitfall trap lids over the weekend. And then trusting me when I needed the car. its towbar and trailer to go up to Tav\liaranui the follcming Monday. This project started on time with a lot of help and support from you. Thanks ,o much to my sisters. Denise. Teresa and Kathryn for all the support and encouragement along the way. The research in this thesis \\as approved bv the ~lassey l.1nivcrsity /\nirnal Ethics Committee ( Protocol 07: 15 ). the Department of C onscrvation (permit :\K-20868-Fi\ U) and the Auckland Regional Council. Funuing vvas provided by the Auckland Regional Council. the Masse, t:nivcrsity '\1astcratc Sc\wlarship and the Guodman Famih· Scholarship. VII Table of Contents Abstract.......................................................................................................................... III Acknowledgements ........................................................................................................... V Table of Contents ........................................................................................................ VIII List of P/ates ................................................................................................................... Xl List of Figures .............................................................................................................. XII List of Tab/es ............................................................................................................... XIII CHAPTER I General Introduction ............................................................................. I 1.1 The evolution of New Zealand's vertebrate fauna .............................. ....................... 2 1.2 Lizard conservation and current issues ...................................................................... 3 1.3 The impacts of invasive species on New Zealand's fauna .......... .. ............................. 9 1.4 Thesis ain1 s and structure .......................................................................................... 12 CHAPTER 2 Tlte impacts of mice (Mus musculus) 011 shore skink.5 (0/igosoma smithi) in a sand dune environment.......................................... .................................... 15 2.1 Abstract .. ............................................................ .................. ........ ............................... 16 2.2 Current kn owledge of mouse impacts on lizards ...... ............... ....... ....... .. ................ 18 2.3 Relevance & aims of current study ................................................... ........................ 20 2.4 Methods ............ ................... ..................................................................... ........ .. .. .. ..... 22 2.4.1 Study species ... ....... ..... ... ...................... .... .... ... ...... ....... .. .............. .. .... ...... ....... .... ... ... ... .... .. 22 2.4.1.1 The Shore skink. (Oligoso111a s111ilhi) (Squamata: Scinicidae) ............. .. ........... 22 2.4. 1.2 T he house mouse (Jfus 111usc11/11s) ..... ....... .... .... ... ..... ..... .. .. 25 2.4.2 Study